619  
FXUS65 KBYZ 221516  
AFDBYZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BILLINGS MT  
916 AM MDT FRI OCT 22 2021  
   
UPDATE
 
 
MORNING SATELLITE IMAGERY SHOWS RIDGE OVER MT WITH AN UPSTREAM  
TROF ALONG THE PACIFIC COAST. AS THE RIDGE AXIS SHIFTS SLOWLY TO  
THE EAST WE WILL SEE INCREASING HIGH CLOUDS TODAY & TONIGHT. BY  
LATE TONIGHT WE COULD SEE SOME LIGHT SHOWERS REACH OUR WESTERN  
MOUNTAINS. OTHERWISE, TODAY WILL BE DRY WITH WARMER THAN NORMAL  
TEMPS (HIGHS IN THE 60S TO LOWER 70S). FORECAST IS IN GOOD SHAPE.  
JKL  
 

 
   
DISCUSSION
 
 
TODAY THROUGH SATURDAY...  
 
HIGH PRESSURE WILL MAINTAIN DRY CONDITIONS OVER THE AREA TODAY,  
BEFORE A PACIFIC WAVE LIFTS INTO WESTERN MONTANA TONIGHT, SHIFTING  
THE RIDGE AXIS TO THE EAST. A FEW LIGHT SHOWERS ARE POSSIBLE OVER  
THE WESTERN MOUNTAINS OVERNIGHT, POTENTIALLY SPREADING OUT ONTO  
THE PLAINS. PATCHY VALLEY FOG IS POSSIBLE NEAR THE DAKOTAS BORDER  
OVERNIGHT. INCREASED CLOUD COVER AND COOLER CONDITIONS CAN BE  
EXPECTED SATURDAY, AS TROUGHING CONTINUES TO MOVE INTO THE REGION.  
RAIN AND SNOW SHOWERS ARE POSSIBLE, MAINLY OVER THE MOUNTAINS  
STARTING SATURDAY AFTERNOON. HIGHS WILL RANGE FROM THE 60S TO  
LOWER 70S TODAY, COOLING INTO THE 50S TO LOWER 60S FOR SATURDAY.  
LOW TEMPERATURES IN THE 30S AND 40S CAN BE EXPECTED TONIGHT. STP  
 
SATURDAY NIGHT THROUGH THURSDAY...  
 
SPLITTING TROUGH WILL BE EXITING THE AREA SATURDAY NIGHT AND EARLY  
SUNDAY. THIS WILL LEAVE BEHIND SOUTHWEST FLOW FOR THE REST OF  
SUNDAY AND MONDAY. ENERGY WILL SWING UP IN SOUTHWEST FLOW AND  
BRING MOISTURE INTO THE HIGHER TERRAIN. LIFT WITH THIS SYSTEM  
SHOULD BE ENOUGH FOR CHANCE POPS MONDAY NIGHT INTO TUESDAY. THE  
STRONGEST PART OF THE TROUGH WILL STAY OVER THE SOUTHERN ROCKIES.  
 
ONCE THE WAVE LEAVES THE AREA, THIS WILL SET UP STRONG WEST TO  
NORTHWEST FLOW BEHIND IT. MID LEVEL WINDS INCREASE WITH A 110 KT  
JET PUNCHING INTO NORTHWEST MONTANA. PART OF THIS JET WILL SLIDE  
ACROSS THE AREA AND THUS, STRONG WIND CHANCES LOOK TO INCREASE  
TUESDAY INTO THURSDAY, WITH THE STRONGEST WINDS LOOKING TO START  
OVER THE WEST TUESDAY AND THEN OVER THE PLAINS WEDNESDAY INTO  
THURSDAY.  
 
TEMPERATURES WILL START OUT MILD (IN THE 60S) SUNDAY AND MONDAY,  
WITH THE WARMEST DAY BEING MONDAY. READINGS WILL COOL BACK DOWN  
INTO THE 50S FOR TUESDAY AND WEDNESDAY. ONE THING THAT IS LACKING  
IN THE EXTENDED FORECAST PACKAGE IS AN INFLUX OF COLD AIR AND A  
POTENTIAL FOR A SOAKING RAIN/SNOW EVENT. TWH  
 

 
   
AVIATION
 
 
VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD WITH  
OCCASIONAL MID AND HIGH CLOUDS. LOCALIZED VALLEY FOG IS POSSIBLE  
AGAIN TONIGHT NEAR THE DAKOTAS BORDER. LOOK FOR SURFACE GUSTS TO  
20-30 KTS AT TIMES ALONG THE WESTERN FOOTHILLS. JKL  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
TDY SAT SUN MON TUE WED THU  
-------------------------------------------------------  
BIL 068 044/060 038/060 042/064 042/058 040/057 038/058  
0/U 11/E 10/B 02/R 52/R 11/N 11/B  
LVM 070 039/055 033/057 038/060 034/052 035/051 031/054  
0/B 22/R 21/B 25/R 62/O 33/R 12/O  
HDN 071 039/062 035/063 036/067 039/060 036/058 035/059  
0/U 11/E 20/B 01/E 53/R 11/B 11/B  
MLS 064 039/058 036/060 038/065 041/058 038/057 036/056  
0/U 11/E 11/B 00/B 43/R 00/N 10/B  
4BQ 065 039/060 039/059 039/069 041/056 036/055 036/056  
0/U 00/B 31/B 00/N 44/R 00/N 10/U  
BHK 061 034/051 035/056 036/059 040/054 035/055 034/054  
0/U 01/N 21/B 00/N 34/R 00/N 00/N  
SHR 069 037/060 033/059 033/067 036/057 033/055 031/057  
0/U 11/E 41/B 01/B 64/R 11/B 11/U  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
WY...NONE.  
 

 
 

 
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